Effects Of Early Pubertal Stress On Schizophrenic Rat Model Induced By Prenatal Immune Activation

BackgroundThe "two-hits" hypothesis of schizophrenia based on neurodevelopmental theory suggests that adverse stress in the critical period of neurodevelopment can cause abnormal brain development,and the combined or accumulated effects of two adverse stresses lead to pathologic activation of the neural loop,leading to disease,this process is more in line with the occurrence and development of schizophrenia.In addition,schizophrenia individuals have immune dysfunction.The occurrence and development of schizophrenia based on secondary shock may be associated with the phenomenon of immune dysfunction related to microglia.ObjectiveIn the critical period of neurodevelopmental development in SD rats,the pregnant rats were infected with polyinsinic acid-polycytidylic acid(Poly(I:C)),and the offspring rats were subjected to 2 weeks of stress,to observe the schizophrenia-like behavior,peripheral and central inflammatory cytokines and inflammatory cells in the brain of offspring rats.To test whether this "two-hits" model" supports the "two-hits" hypothesis of schizophrenia,as well as phenotypic characteristics and immune status in late-puberty of schizophrenia.Methods1.Fifteen male and five female Specific pathogen free(SPF)Sprague-Dawley adultrats at 11-12 weeks were selected for breeding in batches;2.Pregnant rats were randomly divided into pregnancy infection group and control group,respectively,in the 9 days of pregnancy intravenous injection of 10 mg / kg Poly(I:C)and 0.9% of the same volume of saline.After 3 hours of injection,3 samples of each group were randomly selected to detect the protein levels of IL-6 and IL-1? in plasma as quality control to determine the effect of injection;3.The rest pregnant rats live naturally until the birth of the offspring,On postnatal day 21,the pups were weaned,and housed three to four to a cage.The littermate pups were randomly divided into 2 subgroups.In early adolescence(postnatal day 35 to 49),randomly selected 1 subgroup to receive daily forced swimming(4 ° C,4 minutes)or behavioral restrictions(4 hours).At this time,the pups were divided into four groups: PS group(poly(I: C)+ stress),PC group(poly(I: C)+ control),CS group(Control + Stress),CC group(Control + Control);4.In the late stage of adolescence(postnatal day 56),the open-field experiment,the elevated cross-maze experiment,the passive evasion test and the PPI were used to the pups,for detecting the spontaneous activity,anxiety level,learning memory ability and sensory gating Level;5.The levels of IL-6 and IL-1? protein in the pups plasma,prefrontal cortex and hippocampus brain tissue were detected by enzyme linked immunosorbent assay(ELISA)in stage of adolescent;6.The positive expression of calcium-binding protein 1(Iba1)in the prefrontal cortex and hippocampus of the pups in the late stage of adolescence was detected by immunohistochemistry;7.Use the mean ± standard deviation to indicate the measurement data.The data differences between two groups were compared by independent-sample T test,and the data of the four groups were compared by one-way analysis of variance ANOVA.All results were two-sides test,and the size of a test were ? = 0.05.SPSS 23.0 statistical software were used for all the data analysis.Results1.The levels of IL-1? and IL-6 protein in the plasma of pregnant rats treated with poly(I:C)were significantly higher than those of the control group after administration3h(p<0.05);2.In the open field test,the total distance moved of the PS group was longer than that of the PC group?the CS group and CC group.The distance moved in central area of the PS group were longer than the CS group,the CC group.The time moved in central area were longer than the CS group and the CC group.The difference reached statistical significantce(p<0.05),there is no difference between the PS group and the PC group;3.In the elevated plus maze test,the percent open arms entries and the percent open arms times of the PS group was higher than those of the CC group.There was statistically significant difference(p<0.05),there is no difference between the PS group and the PCgroup;4.In step-through passive avoidance test,there was no significant difference in T1 in the four groups(p>0.05).And T of the PS group was significantly lower than that of the CC group,showing statistically significant difference(p<0.05),there is no difference between the PS group and the PC group;5.In prepulse inhibition test,there was no significant difference in the response range to startle inhibition in the four groups(p>0.05).The inhibitory rate to startle inhibition(75dB?80dB?85dB % PPI)of the PS group was statistically significant lower than that of the CC group(p<0.05);6.There was no significant difference in level of plasma IL-6 protein expression in the four groups(p>0.05).The level of plasma IL-1? protein expression in PS group was higher than that in CC group.The level of IL-6 and IL-1? protein expression in prefrontal cortex and hippocampus brain tissue in the PS group was higher than that in the CC group.There was statistically significant difference(p<0.05);7.The OD value of Iba1-labeled microglia in prefrontal cortex and hippocampus of PS group was higher than that of CC group,the difference was statistically significant(p<0.05),and the volume of microglia cells increased,synaptic were shorten and thicken,microglia appears to be actived.Conclusions1.Early pubertal stress to rat model induced by prenatal immune activation inadvance to adolescence to show a more stable,serious behavior and immune function changes.2.Prenatal infection combined early pubertal stress causes schizophrenia-like symptoms in late adolescence rats,including the level of spontaneous activity increased,the level of anxiety decreased?,cognitive function impaired.3.Prenatal infection combined early pubertal stress increased central and peripheral level of inflammatory cytokines in late adolescence rats,and microglia activation in brain.4.Peripheral and central inflammatory status may cause abnormal activation of microglia,which may be an important factor in behavioral abnormalities in rats,providing treatment-related direction.